1. Field of the Invention
The present invention relates to an encoder, a servo unit and an encoder manufacturing method.
2. Description of the Related Art
Encoders are used for measuring the physical quantity, such as the position and the velocity, of a moving object.
The encoders can generally be classified into the rotary encoder and the linear encoder, based on the moving direction of the moving object.
The encoder is also referred to as a rotary position detection device, and detects the position (angle), velocity (rotary velocity) and the like of a moving object (rotary object). On the other hand, the linear encoder is also referred to as a linear position detection device, and detects the position, velocity and the like of a moving object.
The encoders can generally be classified into the incremental encoder and the absolute encoder, based on, e.g., the position detection method. The incremental encoder chiefly detects the relative position of a moving object with reference to the origin position. Specifically, the incremental encoder previously detects the origin position, obtains a periodic signal such as a pulse signal commensurate with the amount of shift from the origin position, and subject the periodic signal to processing such as counting, to thereby detect the position and the like. The absolute encoder is also referred to as the absolute value encoder, and detects the absolute position of a moving object.
The encoders, of a non-contact type, can generally be classified into the “magnetic encoder (including resolvers)” and the “optical encoder”, based on the principle of detection and the like. The magnetic encoder is characterized in its being superior to the optical encoder in the environmental resistance performance, for example. The optical encoder is characterized in its being superior to the magnetic encoder in the position resolution performance, for example. Also developed is an encoder which uses both the magnetism and light so as to exploit the characteristics of both of them (also referred to as the “hybrid encoder”).
Of those various encoders noted above, an encoder of appropriate type is selectively used so as to meet the required characteristic for the intended use. In particular, the encoder plays an important role in grasping the actual position and the like for, e.g., a servo motor that controls the position, the velocity and the like. In other words, the performance, characteristic and the like of a particular encoder selectively used for a servo motor may govern the performance, characteristic and the like of the servo motor.